There are good reasons to stock up big on Postcards. You won't have to worry about running out. You can build a really massive "house of cards" (if you keep your hand steady). And best of all, you'll save a LOAD of money.
Make sure that your background extends to fill the bleed to avoid your Postcards having white edges when trimmed.
This is where we aim to cut your cards.
Make sure any important aspects of your design such as text and logos are inside of the safe area, otherwise they may be cut off.